Summary

The family Ampullaviridae includes viruses with linear dsDNA genomes that replicate in hyperthermophilic archaea from the genus Acidianus. The virions have a unique champagne bottle-shaped morphology and consist of a nucleoprotein filament condensed into a cone-shaped core, which is encased by an envelope, with the base of the ‘bottle’ decorated with a ring of 20 filaments. Genome replication, presumably, is carried out by the virus-encoded protein-primed family B DNA polymerase. The bottle-shaped morphology is unprecedented among viruses of bacteria and eukaryotes and represents a group of archaea-specific virion morphotypes.

Single genus with a single species; two related genomes have been obtained from metagenomics studies

Virion

Morphology

The virion of Acidianus bottle shaped virus (ABV) is enveloped, resembles in its shape a bottle and has an overall length of about 230 nm and a width varying from about 75 nm, at the broad end, to 4 nm, at the pointed end (Figure 1.Ampullaviridae). The broad end of the virion exhibits 20 (±2) thin rigid filaments (20 nm long and 3 nm in width), which appear to be interconnected at their bases and regularly distributed around, and inserted into, a disc or ring. The 9 nm thick envelope encases a cone-shaped core formed by a torroidally supercoiled nucleoprotein filament, 7 nm in width. The bottle-shaped morphology is unprecedented among viruses of bacteria and eukaryotes and represents a group of archaea-specific virion morphotypes [{Prangishvili et al., 2017:29123227RJOHTXPrangishvili et al., 2017, The enigmatic archaeal virosphere, Nat Rev Microbiol, 15, 12, 724-39}].

Physicochemical and physical properties

ABV virion buoyant density in sucrose is about 1.3 g cm−3. The virions are fragile and partially disassembled after high speed ultracentrifugation as well as by prolonged storage. The pointed end of the virion, rather than the broad end, is likely to be involved in adsorption to the host cell surface [{Häring et al., 2005:16014951RJOHTXHäring et al., 2005, Viral diversity in hot springs of Pozzuoli, Italy, and characterization of a unique archaeal virus, Acidianus bottle-shaped virus, from a new family, the Ampullaviridae, J Virol, 79, 15, 9904-11}].

Biology

Acidianus bottle-shaped virus was isolated from a hot acidic spring (87–93 °C, pH 1.5–2.0) in Pozzuoli, Italy. The host range is limited to autochthonous species of hyperthermophilic archaea from the genus Acidianus. ABV virions are released without apparent host cell lysis. Virus infection increases a generation time of the host from about 24 hours to about 48 hours. Release of particles is observed only in the stationary growth phase of the host culture [{Häring et al., 2005:16014951RJOHTXHäring et al., 2005, Viral diversity in hot springs of Pozzuoli, Italy, and characterization of a unique archaeal virus, Acidianus bottle-shaped virus, from a new family, the Ampullaviridae, J Virol, 79, 15, 9904-11}].